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An insulating link is a device used on the hook of a crane to protect the crane operatives from the danger of electrocution should the crane come into contact with a power line. Insulating links are essentially robust insulators and prevent the flow of electricity from bare, suspended wires through cranes and into personnel working near the crane. Variants of insulating links are also made for specific use in antenna guy wires, and foundry and munitions applications. == History == The dangers of working near overhead power lines, which have no insulation covering their wires, first became apparent with the electrification of Western countries in the first half of the twentieth century. As early as 1931〔Kraner H.M. Westinghouse Electric & MFG CO. 1931. Insulator. United States. Patent US 1813172〕 there was a patent for an insulator that could be affixed to a crane’s wire rope or chain in order to prevent electrocution. Such early designs, however, proved unreliable because of their inability to operate safely in all construction crane environments. By 1965 Federal law mandated the use of insulating links on cranes in the United States. However, this requirement was lifted in the 1980s after an investigation found that lethal levels of electric current could pass through the insulating links in use at that time if they were wet or otherwise contaminated.〔Morgan D., Hamilton H. 1982. Evaluation of links for safety applications. National Crane legal defence. s.l.: s.n.〕 This problem meant that insulating links were not widely used until new designs were developed in the 1990s. New developments in insulating link technology, that take account of the likelihood of insulating links being used in the typically dirty and wet construction industry environment, meant that the US Government introduced a new law〔(【引用サイトリンク】title=Occupational Safety And Health Administration: Small Entity Compliance Guide For Final Rule For Cranes And Derricks In Construction )〕 in 2010 that mandates the use of approved insulating links in certain situations. These insulating links must be tested and approved by a Nationally Recognized Testing Laboratory to a standard such as UL2737.〔(【引用サイトリンク】title=ELRK.GuideInfo Crane Equipment Over 600 Volts )〕 UL2737 has incorporated tests which recognize that the current flowing over a contaminated and wet insulating links has bursts of current trying to jump over "dry bands", as shown in figure 2. Dry banding results from the current passing over the contaminated and moist insulator, heating and drying out the water, usually at points of minimum diameter and radius. If the burst of current occurs in the vulnerable T wave of the heart cycle then fibrillation may occur. The methodology of analysis used in UL2737 applies the principals from IEC 60479-2, shown in figure 3, to design a testing protocol to determine if the insulating link is safe in the construction crane environment where rain and contamination, SP3, are normative. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Insulating link」の詳細全文を読む スポンサード リンク
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